Effect of trap-assisted recombination on open-circuit voltage loss in phthalocyanine/fullerene solar cells

• Published in: Organic electronics Vol. 55; pp. 69 - 74
• Main Authors: Shintaku, Naoto, Hiramoto, Masahiro, Izawa, Seiichiro
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2018
• Subjects: Charge recombination; Open-circuit voltage; Organic solar cell; Charge recombination; Organic solar cell; Open-circuit voltage
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2018.01.016

Large energy losses in open-circuit voltage (VOC) are still an issue for the photo-conversion efficiency of organic solar cells (OSCs). We clarify the relationship between charge recombination and VOC loss for phthalocyanine/fullerene planar heterojunction (PHJ) OSCs. We quantify the VOC loss relative to the charge-transfer state energy by the temperature dependence of VOC. The charge recombination order obtained from impedance measurements indicates the presence of trap-assisted recombination. Our results suggest that the VOC losses are caused by the broad distribution of the tail state near the donor/acceptor (D/A) interface in the PHJ device. Thus, reducing the number of trap states near the D/A interface could lead to an increase in VOC. Trap-assisted recombination causes open-circuit voltage loss. [Display omitted] •Relationship between charge recombination and voltage loss was clarified.•Temperature dependence of recombination order was estimated by impedance measurement.•Trap states near donor/acceptor interface play a key role in voltage loss.